.TH std::data 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::data \- std::data

.SH Synopsis
   Defined in header <array>
   Defined in header <deque>
   Defined in header <flat_map>
   Defined in header <flat_set>
   Defined in header <forward_list>
   Defined in header <iterator>
   Defined in header <list>
   Defined in header <map>
   Defined in header <regex>
   Defined in header <set>
   Defined in header <span>
   Defined in header <string>
   Defined in header <string_view>
   Defined in header <unordered_map>
   Defined in header <unordered_set>
   Defined in header <vector>
   template< class C >                                              \fB(1)\fP \fI(since C++17)\fP
   constexpr auto data( C& c ) -> decltype(c.data());
   template< class C >                                              \fB(2)\fP \fI(since C++17)\fP
   constexpr auto data( const C& c ) -> decltype(c.data());
   template< class T, std::size_t N >                               \fB(3)\fP \fI(since C++17)\fP
   constexpr T* data( T (&array)[N] ) noexcept;
   template< class E >                                              \fB(4)\fP \fI(since C++17)\fP
   constexpr const E* data( std::initializer_list<E> il ) noexcept;

   Returns a pointer to the block of memory containing the elements of the range.

   1,2) Returns c.data().
   3) Returns array.
   4) Returns il.begin().

.SH Parameters

   c     - a container or view with a data() member function
   array - an array of arbitrary type
   il    - an std::initializer_list

.SH Return value

   1,2) c.data()
   3) array
   4) il.begin()

.SH Exceptions

   1) May throw implementation-defined exceptions.

.SH Notes

   The overload for std::initializer_list is necessary because it does not have a
   member function data.

            Feature-test macro           Value    Std               Feature
   __cpp_lib_nonmember_container_access 201411L \fI(C++17)\fP std::size(), std::data(), and
                                                        std::empty()

.SH Possible implementation

.SH First version
   template<class C>
   constexpr auto data(C& c) -> decltype(c.data())
   {
       return c.data();
   }
.SH Second version
   template<class C>
   constexpr auto data(const C& c) -> decltype(c.data())
   {
       return c.data();
   }
                           Third version
   template<class T, std::size_t N>
   constexpr T* data(T (&array)[N]) noexcept
   {
       return array;
   }
                          Fourth version
   template<class E>
   constexpr const E* data(std::initializer_list<E> il) noexcept
   {
       return il.begin();
   }

.SH Example


// Run this code

 #include <cstring>
 #include <iostream>
 #include <string>

 int main()
 {
     std::string s{"Hello world!\\n"};

     char a[20]; // storage for a C-style string
     std::strcpy(a, std::data(s));
 //  [s.data(), s.data() + s.size()] is guaranteed to be an NTBS since C++11

     std::cout << a;
 }

.SH Output:

 Hello world!

.SH See also

   ranges::data  obtains a pointer to the beginning of a contiguous range
   (C++20)       (customization point object)
   ranges::cdata obtains a pointer to the beginning of a read-only contiguous range
   (C++20)       (customization point object)
